Glow discharge tube for use for example in recording sound



March 17, 1936. R. B. MORGAN 2,034,148

GLOW DISCHARGE TUBE FOR USE. FOR EXAMPLE IN RECORDING SOUND Filed Jan. 6, 1930 Patented Mar. 17, 1936 UNITED STATES PATENT OFFICE GLOW DISCHARGE TUBE FOR USE FOR EXAMPLE IN RECORDING SOUND ration of Delaware Application January 6, 1930, Serial No. 418,920 In Great Britain February 12, 1929 Claims.

The present invention relates to glow discharge tubes and more particularly to the use of such tubes in the recording or transmitting of mechanical or electrical oscillations with the aid of light.

According to the present invention, light, modulated in intensity in accordance with electrical or mechanical oscillations, is generated by means of a discharge tube the light from which is magnetically controlled or influenced.

The invention further provides a discharge device comprising an envelope containing mercury vapour and having disposed therein a filamentary cathode, an anode surrounding said cathode, and a coil arranged around said envelope, said filamentary cathode lying substantially along the axis of said coil.

The invention is illustrated by way of example in the accompanying drawing in which Figs. 1 and 2 show views in part sectional side elevation and in end elevation respectively of a discharge tube in accordance with the invention, and

Figs. 3 and 4 illustrate diagrammatically two circuit arrangements according to the invention.

Referring to Figs. 1 and 2, an envelope l, which may be of quartz or glass, is filled with mercury vapour at a suitable pressure. Within the envelope I are mounted a filamentary cathode 2 of helical shape and a cylindrical anode 3 (for example of nickel) surrounding the cathode 2. Around the outside of the envelope I is fixed a coil 4. The filament 2 lies along the axis of the coil 4. In this way, when current is passed through the coil 4, a magnetic field is established in the discharge space around the filament 2 and parallel to the filament axis. The effect of this magnetic field is greatly to intensify the light emitted and to concentrate it in an axial direction.

Referring to Fig. 3, in which like parts are given the same references as in Fig. 1, the anode 3 is connected through a choke coil 5 to a point of positive potential relative to the cathode 2. The potential difference between the anode 3 and the cathode 2 may, for example, be about 20 volts.

When applying the arrangement described to the recording of sound, electrical oscillations from a microphone are impressed, after suitable amplification, on the coil 4. A steady direct current is also passed through the coil 4 or through a separate coil arranged coaxially therewith. The value of this direct current is so adjusted that the steady magnetic field produced thereby brings the tube into such a state that a small change of field strength produces a large change in the light emitted in a direction axially of the coil in accordance with a linear relation. When ad- These variations indrical column of light extending as far as the wall of the envelope.

In the circuit of Fig. 3, the choke coil 5 serves to prevent alternating currents generated be- 1 tween the electrodes, 2, 3 of the tube from flowing through the anode current source. As shown in dotted lines, these oscillations may be used with or without amplification to operate a monitoring device such as a loudspeaker 6.

Referring now to Fig. 4, instead of varying the intensity of the magnetic field produced by the coil 4, this field is maintained constant and the light variations are .obtained by impressing elec-.. trical oscillations upon the electrodes of the tube. The magnetic field, nevertheless, influences the light emitted by greatly increasing the intensity of the glow. The anode 3 is connected, as before, through a choke 5 to a positive potential point, and the coil 4 is fed with direct current from a source 1, the value of this current being adjustable by means of the variable resistance 8. Electrical oscillations, which may be derived as before from a microphone, are impressed upon the primary winding of the transformer 9 and in this way an alternating potential difference is applied through the blocking condenser Ill between the two electrodes 2, 3 and modulates the steady potential between them.

Although the invention has been described with particular reference to sound recording, it may be applied to other purposes.

When, for example, the apparatus is used for transmitting oscillations with the aid of light from one station to anothenthe light from the sending station may be allowed to fall upon a photo-sensitive device at the receiving station.

The apparatus may also be used in connection with the receiving station of a television or phototelegraphic system, the incoming electrical oscillations being impressed upon the discharge device and producing corresponding changes in the intensity of the light emitted. In combination with a suitable scanning device, therefore, the apparatus may be used to build up at the sending stat Qn the picture or view transmitted.

The invention may also be applied to the generation of light of varying intensity from mechanical oscillations without first converting the mechanical oscillations into electrical oscillations. For example, the magnetic field in the discharge space may be established by or through a member which is capable of vibration. The mechanical vibrations of this member can be made to produce variations in the intensity of the magnetic field around the filament. Clearly, this can be done either by arranging that the mechanical oscillations effect a change in the intensity of the magnetic field or else by causing the mechanical oscillations to change the position of the magnetic field and thus alter the intensity of the field around the cathode although the overall intensity of the field may remain constant. A combination of these two effects can also be used.

It has been found that, after the tube of the type described has commenced to glow, the current for heating the filament may frequently be interrupted without interfering with the behaviour of the tube. The filament may in some cases be replaced by a cold electrode, separate ionizing means being provided within the tube to initiate the discharge.

I claim:

1. The method of photographically recording mechanical impulses by means of a gaseous electric discharge device of the type wherein electrons are caused to ionize the gas by radial flow from a central thermionic electrode toward a surrounding anode, which comprises translating the mechanical impulses into electrical impulses, causing said electrical impulses to vary the radial fiow of the electrons from the cathode to the anode, whereby varying light impulses are produced, and recording the light impulses upon a photo-sensitive surface.

2. The method of photographically recording mechanical impulses by means of a gaseous electric discharge device of the type wherein electrons are caused to ionize the gas by radial flow from a central thermionic electrode toward a surrounding anode, which comprises translating the mechanical impulses into a fluctuating magnetic field, causing said field to variably oppose the radial fiow of electrons, whereby the ionization of the gas and the light emitted thereby are caused to vary, and recording the light emitted by the device on a photo-sensitive material.

3. In a system for photographically recording electrical impulses, a gaseous glow-discharge device of the type wherein a central thermionic cathode is surrounded by an anode, means for impressing unidirectional positive potentials on the anode with respect to the cathode to cause emitted electrons to fiow substantially radially toward said anode, and means for setting up a magnetic field substantially coaxial with the anode, whereby the emitted electrons may be caused to depart from radial paths to vary the ionization of the gas either by varying the unidirectional potential or the strength of the magnetic field.

4. In a system for photographically recording impulses, a glow discharge device comprising a thermionic cathode and an anode, means for causing a flow of electrons therebetween, magnetic means for influencing said flow of electrons, and means independent of said magnetic means and responsive to said impulses for varying the flow of said electrons whereby the glow of said device is made to correspond to the impulses being recorded.

5. In a system of the character described, an electron discharge device including a thermionic cathode and an anode, means for applying a constant potential across said electrodes, means for influencing the operating condition of said device, and means independent of said firstnamed means and responsive to a variable effect for varying the level of said potential in accordance with variations in said eifect.

RAYMOND BAINBRIDGE MORGAN. 

